Submicro-facet light-emitting device and method for fabricating the same

Abstract

A light emitting device comprises an n-type layer, a p-type layer, and an active region sandwiched between the n-type layer and the p-type layer, wherein the active-region has a wavy structure with nano or micro fluctuations in its thickness direction. The n-type layer comprises crystal facets on its upper surface, and the active-region is conformally formed on the upper surface of the n-type layer and substantially follows the shape of the crystal facets so as to form the wavy structure. A method for fabricating the same is also provided.

What is claimed is: 
     
       1. A light emitting device comprising:
 an n-type layer; 
 a p-type layer; 
 an active region sandwiched between the n-type layer and the p-type layer; 
 wherein the active-region has a wavy structure with nano or micro fluctuations in its thickness direction; 
 wherein the n-type layer comprises crystal facets on its upper surface, and the active-region is conformally formed on the upper surface of the n-type layer and substantially follows the shape of the crystal facets so as to form the wavy structure; 
 wherein the n-type layer comprises (00.1)-oriented III-nitride pillars and the crystal facets are formed on top of the (00.1)-oriented III-nitride pillars, wherein each of the pillars provides six facets due to six-fold crystal structure symmetry; or the n-type layer comprises (111)-oriented III-nitride pillars and the crystal facets are formed on top of the (111)-oriented III-nitride pillars, wherein each of the pillars provides four facets due to four-fold crystal structure symmetry; and 
 wherein the (00.1)-oriented III-nitride pillars contain a strain-modulation structure which contains a silicon concentration peak of above 5×10 19  cm −3  with a full-width at half-maximum (FWHM) of 15-20 nm, when being measured by a depth profiling metrology such as secondary ion mass spectrometry (SIMS). 
 
     
     
       2. The light-emitting device according to  claim 1 , wherein the (00.1)-oriented III-nitride pillars are arranged in a hexagonal lattice pattern with a lattice constant of 150 nm to 1000 nm and the diameter of the pillars is from 140 nm to 1000 nm. 
     
     
       3. The light-emitting device according to  claim 2 , wherein the (00.1)-oriented III-nitride pillars have a density of 5×10 8  cm −2  to 5×10 9  cm −2 . 
     
     
       4. The light-emitting device according to  claim 1 , wherein the (00.1)-oriented III-nitride pillars contain an AlGaN/GaN superlattice structure, with Al-fraction not less than 20%, or contain a GaN/InGaN superlattice structure, with In-fraction not less than 4%. 
     
     
       5. The light-emitting device according to  claim 1 , wherein gaps are formed between neighboring (00.1)-oriented III-nitride pillars. 
     
     
       6. The light-emitting device according to  claim 1 , wherein the (00.1)-oriented III-nitride pillars have a height larger than 500 nm. 
     
     
       7. The light-emitting device according to  claim 1 , further comprising a mask layer embedded in the n-type layer, wherein the mask layer consists of a growth suppression area and a growth seeding area formed by nano-scale openings, and the (00.1)-oriented III-nitride pillars grow from and penetrate through the openings. 
     
     
       8. The light-emitting device according to  claim 2 , wherein the (00.1)-oriented III-nitride pillars are arranged in a hexagonal lattice pattern with a lattice constant of 150 nm to 500 nm and the diameter of the pillars is from 140 nm to 500 nm. 
     
     
       9. The light-emitting device according to  claim 1 , wherein the crystal facets comprise (10.1) facets or (11.1) facets. 
     
     
       10. A light emitting device comprising:
 an n-type layer comprising pillars extruding along a thickness direction of the n-type layer, wherein each of the pillars has a pillar body and a tapering pillar top formed on top of the pillar body, and the tapering pillar top has crystal facets; 
 a p-type layer; 
 an active region sandwiched between the n-type layer and the p-type layer; 
 wherein the active-region has a wavy structure with nano or micro fluctuations in its thickness direction, the active-region is conformally formed on the crystal facets of the tapering pillar tops of the pillars and substantially follows the shape of the crystal facets so as to form the wavy structure; 
 wherein the pillars are formed from (00.1)-oriented III-nitride, and each of the pillar tops contains six crystal facets due to six-fold crystal structure symmetry; or the pillars are form from (111)-oriented III-nitride, and each of the pillar tops contains four facets due to four-fold crystal structure symmetry; 
 wherein the pillars formed from (00.1)-oriented III-nitride contain a strain-modulation structure which contains a silicon concentration peak of above 5×10 19  cm −3  with a full-width at half-maximum (FWHM) of 15-20 nm, when being measured by a depth profiling metrology such as secondary ion mass spectrometry (SIMS). 
 
     
     
       11. The light-emitting device according to  claim 5 , wherein the gaps between neighboring (00.1)-oriented III-nitride pillars have a dimension of 3-200 nm.